The present invention relates to an image display apparatus used in a tomographic apparatus such as an X-ray CT (computed tomographic) apparatus or a magnetic resonance imaging system (MRI system).
In an imaging system of, e.g., an X-ray CT apparatus or an MRI system, an image display apparatus is used for displaying an image.
In the image display apparatus of this type, cine display (motion display) for displaying motion of a stomach or a heart as motion pictures is performed.
The cine display of an image in, for example, a 512.sup.2 (512.times.512) matrix corresponds to sequential display of 20 to 30 still images per second. For the cine display in a conventional image display system, if a series of images (still images sequentially displayed to display each image for a predetermined period of time) to be recognized as substantially a one-frame still image is given to an image unit, image information corresponding to 20 to 30 still images of the 512.sup.2 matrix per image unit is stored in a memory, and the 20 to 30 still images, data of which are stored in the memory, are switched at high speed and displayed. Therefore, in order to perform cine display, a very large capacity memory must be used, and the image stored in the memory must be switched at high speed and displayed. For this reason, it is very difficult to realize an image display apparatus.
Furthermore, when window processing is performed for the image information (gradation is provided in a specific gray level range of the original image data), a larger capacity memory than that described above is required, and the memory switching access becomes more complicated. Image write/read access with respect to the memory and window processing are performed by a common central processing unit (CPU). Therefore, an image display switching speed is considerably decreased. For this reason, it is still more difficult to realize the image display apparatus.